Accommodating intraocular lenses and associated systems, frames, and methods

ABSTRACT

An intraocular lens for providing accommodative vision to a subject includes a frame disposed about an optical axis, a first optical element, a second optical element, and a connecting element operably coupling the frame to the optical elements. The frame comprises an anterior frame element and a posterior frame element. The connecting element is configured to convert a first displacement between the frame elements in a direction that is substantially parallel to the optical axis into a second displacement between the optical elements that is substantially perpendicular to the optical axis. The second displacement may be translational and/or rotation. In some embodiments, the optical elements are two varifocal lenses.

RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119(e) toprovisional application No. 60/871,632, filed on Dec. 22, 2006, toEuropean application no. 06127102.9 filed on Dec. 22, 2006, and to PCTapplication no. PCT/EP2007/063827, filed on 12 Dec. 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to intraocular lenses and morespecifically to accommodating intraocular lenses.

2. Description of the Related Art

In a natural eye, the accommodative power, i.e. the ability to(dynamically) vary the focal length of the lens and thus of the eye as awhole, is provided by the reversible deformation of the lens betweenmore and less curved shapes. The natural lens comprises a crystallinelens in a lens capsule or capsular bag. The capsular bag is connected tothe so-called zonulae. The zonulae extend generally radially from thelens and are connected with their other end to the ciliary muscle whichsurrounds the eye essentially in the equatorial plane. The natural lensis generally resilient and strives to a generally more spherical shape.

In the relaxed state of the ciliary muscle its diameter is relativelywide. This causes the zonulae to pull on the capsular bag and to flattenthe lens against its resilience. In a young, healthy human eye withoutrefractive errors, this causes the eye to become emmetropic, i.e. havingacute vision in “infinity” in a desaccommodated state. Emmetropy isusually determined by having a patient read a predetermined line of aneye-chart from a distance of approximately 5 metres.

When the ciliary muscle contracts, its inner diameter reduces, thusreducing the tension in the zonulae. As a consequence, the natural lensrelaxes to assume a shape with a stronger curvature. Thus, the focalpower of the lens is increased and the eye can focus on shorterdistances, e.g. for reading.

Due to aging or an affliction, the natural lens may lose some orsubstantially all of its resiliency and only allow accommodation over alimited scope, e.g. resulting in age-related far-sightedness orpresbyopia.

Several optical surgery procedures, e.g. cataract surgery, involve theremoval of the natural crystalline lens of an eye. In order to installor restore vision to the patient after such surgery an artificial lensmay be implanted in the eye. Presently, most implanted artificial lenseshave a fixed focal length or are multi-focal lenses having two or morefixed focal lengths. These lens types provide no or at mostpseudo-accommodative power. This leaves patients who have underwent suchsurgery more or less handicapped in everyday life, since they are nolonger able to quickly and rapidly focus at any given distance.

When the natural crystalline lens is surgically removed from the lenscapsule, the capsular bag may be left essentially intact, in that it canstill be deformed by the ciliary muscle if a sufficient counterforce isprovided. This functionality can remain even when a substantial window,or rhexis, has been cut out of the capsular bag.

There is thus ongoing research for an artificial intraocular lens orlens system providing accommodative power, especially by using thenatural focussing system of the eye, relying on the reversibledeformation of the lens, and a number of patent applications and patentsdiscuss accommodating intraocular lenses.

For instance, U.S. Pat. No. 4,994,082, US and 2004/0158322 discusscomplex lens systems mounted in a frame wherein the individual lensesmove with respect to each other essentially in a plane perpendicular tothe optical axis. U.S. Pat. No. 4,994,082 also discusses displacing twolenses along the optical axis.

Furthermore, U.S. Pat. No. 5,275,623, US 2002/0116061, US 2004/0082994and US 2005/055092 discuss an accommodating intraocular lens comprisinga frame and two lenses which are displaced along the optical axis of thelens system and of the eye, wherein the relative motion of the anteriorand posterior parts of the capsular bag is used for realising the motionof the lenses.

US 2005/0131535 discusses a deformable intraocular lens in a frame.

It should be noted that U.S. Pat. No. 3,305,294 U.S. Pat. No. 3,507,565,U.S. Pat. No. 3,583,790, U.S. Pat. No. 3,617,116, U.S. Pat. No.3,632,696, U.S. Pat. No. 3,751,138, U.S. Pat. No. 3,827,798 and U.S.Pat. No. 4,457,592 describe changing the focal length of a lens systemcomprising two particularly shaped lenses by linearly displacing thelenses with respect to each other.

Using such lenses for intraocular lenses is known from WO 2005/084587,WO 2006/025726, WO 2006/118452 and from Simonov A N, Vdovin G, Rombach MC, Opt Expr 2006; 14:7757-7775.

U.S. Pat. No. 4,650,292 discusses rotating optical elements of acompound lens with respect to each other for changing the focal lengththereof, using surfaces described by polynomial equations having anon-zero term of at least fourth order.

Further, U.S. Pat. No. 6,598,606 describes a method for providing a lensimplant in a lens capsule with a predetermined refractive value.

In all these prior art (intraocular) lenses and lens system relativelylarge displacements of the lenses with respect to each other are usedfor accommodating and/or the intraocular lenses use the equatorialmotion of the zonulae and/or capsular bag for effecting accommodation.

It has been found that when an artificial lens has been implanted intothe capsular bag, the flexibility of the capsular bag, and thus itsaccommodative power reduces over time, which effect is usually mostpronounced around the equatorial rim of the capsular bag.

Further, it has been found that in time, cellular growth or migrationmay cause further stiffening of (the remainder of) the capsular bag andopacification thereof, and consequentially not only loss ofaccommodative power but also general loss of sight to the patient.

SUMMARY OF THE INVENTION

An object of the present invention is to provide improvements forartificial intraocular lenses, in particular for accommodatingintraocular lenses. One aspect of the present invention involvesintraocular lenses with associated frames or support structures forproviding relative motion between at least two optical elements, therelative motion providing a change in focal length or accommodation ofthe intraocular lenses.

In one embodiment, an intraocular frame for implantation in the capsularbag of an eye comprises an anterior frame element, a posterior frameelement, and one or more connecting elements. The frame elements aredisposed about an optical axis. The connecting element is configured tooperably couple the frame elements to first and second optical elements.The connecting element is further configured to convert a firstdisplacement between the frame elements in a direction that issubstantially parallel to the optical axis into a second displacementbetween the optical elements, the second displacement beingsubstantially perpendicular to the optical axis.

The first displacement is preferably substantially parallel to theoptical axis of the eye. The second displacement is preferablysubstantially perpendicular to the first displacement and substantiallyperpendicular to the optical axis of the eye.

The frame may also include a resilient element for urging the anteriorand posterior frame elements towards a predetermined axial separation.The predetermined axial separation may be chosen such that the anteriorand posterior frame elements are urged against the anterior andposterior inner wall, respectively, of the capsular bag when implantedtherein.

The resilient element may be configured to bias the anterior andposterior frame elements against the anterior and posterior inner wall,respectively, of the capsular bag when implanted therein. Accordingly,the first displacement of the anterior and posterior frame elements willbe caused by the action of the capsular bag under the influence of theciliary muscle. Such a frame is thus beneficial in that the motion ofthe capsular bag in the direction of the optical axis is coupled with amotion of an optical element at least partially in a perpendiculardirection thereto. Thus, the frame may mimic the resilient behaviour ofthe natural lens in this respect.

This contrasts other accommodating intraocular lenses, which may eitherrely on the equatorial motion and/or close contact to the equatorial rimof the capsular bag and the zonulae for moving optical elements in thisplane, or which rely on the motion essentially along the optical axisfor moving optical elements in the same direction.

The conversion between the first and second displacements may be causedby a mounting element which is configured to be attached, in use, to anoptical element and which may rotate, bend or slide etc., e.g. againstanother part of the frame or against an inner wall of the capsular bag,upon a displacement of the anterior and posterior frame elements withrespect to each other having a component parallel to the optical axis ofthe eye.

In the frame, the resilient element and the connecting element may bethe same, thus reducing the complexity of the device.

In an efficient embodiment, the connecting element of the frame isarranged for converting the first displacement into the seconddisplacement.

In this case, the optical element is, in use, attached between andpreferably free from the anterior and posterior frame elements so thatit may be essentially immovable along the optical axis, or so that itsdisplacement may be essentially solely determined by the connectingelement.

The connecting element may be e.g. an axial torsion-spring orientedsubstantially parallel to the optical axis, which is wound up or down bythe first displacement of the anterior and posterior frame elements andwhich therewith displaces the optical element essentially perpendicularto the optical axis. The spring is preferably symmetric about theconnection to the optical element.

In a preferred embodiment, the connecting element has a deflection froma straight connection between the anterior and posterior frame elements.The deflection may be a hinge, a fold or a resilient curve etc. In thismanner, a preferred location is provided which will flex or bend etc.and thus be displaced under the influence of the displacement of theanterior and posterior frame elements with respect to each other. Themagnitude of the component of the displacement perpendicular to theoptical axis is dependent on the position along the connecting element;the element will generally be substantially immobile relative to theframe at or near the connection to the anterior and posterior frameelements, respectively, and be maximum at the hinge, fold or curve.Thus, it is preferred that the connecting element is configured to beattached to an optical element at least near the point of maximumdeflection from a straight connection between the anterior and posteriorframe elements, where the response to a displacement of the anterior andposterior frame elements is maximised.

The point of maximum deflection may be in the middle of, or at anotherposition along, the length of the connecting element.

In order to cause a substantially radial component to the seconddisplacement, the deflection of the connecting element may have a radialcomponent with respect to the optical axis of the eye.

It is generally preferred that at least the anterior frame elementprovides an opening for allowing aqueous humor to pass therethrough,preferably for allowing aqueous humor to flow between the anteriorchamber of the eye and the interior of the capsular bag. This isconsidered beneficial, since it is believed that the aqueous humor hashealing properties for the capsular bag in that it reduces or evenprevents scar-tissue build-up or generally proliferation of cells on thecapsular bag, which might lead to opacity of the capsular bag andsubsequent loss of vision. It is therefore preferred that also theposterior frame element is provided with such an opening for allowingaqueous humor to pass therethrough. Depending on the optical propertiesof the frame, the opening is obviously best situated so as not to blockvision.

Efficiently, at least the posterior frame element is provided with arelatively sharp edge along the contact region of the frame element withthe wall of the capsular bag. A relatively sharp edge or rim, as opposedto a smoothly rounded one, hinders cellular growth or migration whichmay occur outside the posterior frame element from passing within aperimeter set by the edge, thus reducing or even preventing cellulargrowth on and subsequent opacification of the inside of the contactregion.

The edge or rim may be essentially square- or acute-angled or even beslightly rounded and still exhibit the cell growth blocking effect. Suchroundness of the edge may be determined by the deviation of the edgefrom a square angle. An edge with a fillet due to polishing resulting adeviation of up to 13.5 micron has been found to effectively obstructcell migration across the edge. (Tetz M, Wildeck A. Evaluating anddefining the sharpness of intraocular lenses. Part 1: influence of opticdesign on the growth of the lens epithelial cells in vitro. J CataractRefract Surg, 2005; 31:2172-2179)

The frame may comprise elements for substantially centering the frameabout the optical axis of the eye when implanted therein. Such elements,e.g. haptics, preferably exert no or very low pressure against theequatorial rim of the eye, e.g. just sufficient to keep the frame inplace.

It has been observed that the loss of resiliency and flexibility of thecapsular bag once an intraocular lens has been implanted therein is mostpronounced about the equatorial rim. It is the inventors' believe thatthe stiffening of the capsular bag may be caused in response to thestress exerted on the capsular bag by the implanted lens. Thus, lenseswhich stretch or tauten the capsular bag in the radial direction andwhich rely on a variation in the diameter of the capsular bag foraccommodation may cause a deterioration of the function of the capsularbag. It may therefore be preferred not to exert such stress. In apreferred embodiment, therefore, the frame, once implanted in thecapsular bag of the eye, is only in contact with the interior surfacethereof on the anterior and posterior walls thereof and is free fromcontact with the equatorial rim thereof. In such embodiments the framemay be configured to be free from such contact both in the accommodatedand desaccommodated states as well as in any transitional state.

The frame may also comprise different or additional elements, such asprotrusions, legs, rings or wings etc. for securing the position of theframe with respect to the capsular bag.

Preferably, with a frame according to an embodiment of the presentinvention the net effect of the forces on the capsular bag is togenerally urge the capsular bag towards the accommodating shape. Thus,the natural resiliency of the eye may be mimicked, which may lead tomaintain the natural accommodating effect and efficiency of the eye forlonger periods than is found with present intraocular devices.

Within this text, the equatorial rim is considered to be the part of thecapsular bag to which the zonulae are attached. In an adult human eyethis part usually extends for about 2.5 mm from the equatorial planewhich extends through the maximum girth of the capsular bag, bothlengths measured along the surface of the capsular bag. The anterior andposterior sections of the capsular bag are considered the parts anteriorand posterior of the equatorial rim, respectively.

Another aspect of the present invention is an intraocular lens forimplantation in the capsular bag of an eye having an optical axis. Theintraocular lens comprises an optical system attached, in use, to afirst connecting element of a frame according to an embodiment of thepresent invention.

The optical system may thus be substantially free from contact to thewalls of the capsular bag, which allows aqueous humor to flowessentially unimpeded around the optical system. Thus, the capsular bagmay be passivated or appeased, as described before, preventingstiffening and opacification thereof. Further, the aqueous humor mayrinse the optical system with every movement or deformation of thecapsular bag and/or the optical system, which is thought to reduce thesticking of cells to the surfaces of the optical system and thusclouding it and therewith possibly impairing vision. In addition, theoptical system may be displaced in response to the displacement of theanterior and posterior frame elements and the capsular bag,respectively, which may be used for accommodation.

The optical system is preferably additionally attached, in use, to atleast a second connecting element of the frame, so that the positionand/or displacement of the optical system is better and more robustlydefined and maintained than in the case the system is attached to asingle point.

In a beneficial embodiment of the present invention, the optical systemis reversibly deformable by the displacement of at least one of theparts thereof which is attached to a connecting element of the frame.Deforming an optical system usually allows to modify its opticalproperties. Thus, the intraocular lens according to an embodiment of thepresent invention may be an accommodating lens.

In this case, it is preferred that the optical system comprises areversibly deformable lens. This allows to mimic the natural eye quiteclosely. The equatorial pulling force on the lens capsule of a resilientlens by the zonulae may be replaced by the equatorial pulling bycorresponding elements of the frame on the artificial lens. Theresiliency of the natural lens which urges the capsule to theaccommodating configuration and which is lost upon the removal of thecrystalline lens is replaced by that of the artificial lens and/or ofthe frame. The various resiliencies of the different elements may bechosen or configured so as to emulate the forces of the natural eye.

Another preferred optical system comprises at least two optical elementswhich are movable with respect to each other. This allows to properlydesign a particular optical configuration and to predict the effect of arelative displacement of the optical elements with respect to eachother. The geometric shape and/or material of the optical elements,preferably lenses, may be chosen at will so as to achieve a desiredeffect.

It is preferred that the at least two optical elements are mutuallymovably interconnected, so that the relative position and/or motion ofthe elements may be better defined than generally possible without theinterconnection.

The interconnection may provide a centre of rotation for at least twoindividual optical elements with respect to each other. This allows awell defined rotation of the elements with respect to each other about acommon axis.

It is preferred that the optical system comprises at least one resilientelement for providing a restoring force for urging the optical system toa default configuration. Thus, the optical system may have a preferredposition to which it strives to return. This may increase the similarityof the artificial lens to a natural lens. The default position may be anaccommodating position.

The optical system may be provided with at least one element fordefining a default configuration. The element may comprise one or morestops for arresting the optical system in this default configuration, orit may be a resilient element having a neutral position etc. This allowsdefinition of a particular optical property, such as a focal length, ofthe optical system, and to reliably retrieve the configuration for whichthe property was defined.

This default configuration defined by the at least one element need notbe the configuration to which the intraocular lens or the optical systemstrives; the intraocular lens or the optical system may have a defaultconfiguration for achieving emmetropy and one for an accommodated state.

The intraocular lens according to an embodiment of the present inventionis preferably arranged so that the net effect of the forces on thecapsular bag, at least due to the at least one resilient element of theframe and/or to the at least one resilient element for providing arestoring force for urging the optical system to a defaultconfiguration, is to generally urge the capsular bag towards theaccommodating shape. Thus the artificial intraocular lens behaves muchlike the natural lens. The main contribution to the force, either fromthe frame, the optical system or another element may be chosen, e.g. tosuit particular or structural preferences or demands.

According to an aspect of the present invention an intraocular lens isprovided comprising a frame and an optical system. The frame comprisesan anterior frame element, a posterior frame element, and a first and asecond connecting element connecting the anterior and posterior frameelements. The first and second connecting element are configured to beattached, in use, to an optical system. The frame is configured forconverting a first displacement of the anterior and posterior frameelements with respect to each other having at least a component parallelto the optical axis of the eye into a second displacement of at least apart of the optical element, the second displacement having at least acomponent perpendicular to the optical axis of the eye. The opticalsystem is an optical system as disclosed above which is resilient. Thenet effect of the forces on the capsular bag due to the intraocular lensis to generally urge the capsular bag towards the accommodating shape.

Such an intraocular lens combines the benefits of the embodiments of theintraocular lens discussed above with that of a frame, wherein the framemay be a passive device and need not have a resilient element. The netforce of such an intraocular lens may be efficiently optimised, as itoriginates in the resiliency characteristics of the optical system.

Within this text, a lens may be diffractive, refractive or a combinationwhich may have positive and negative value, but which may also have zerooptical strength. Graded index lenses, Fresnel lenses etc. andnon-rotationally symmetric lenses, e.g. cylinder lenses, are alsoincluded. An optical system may comprise one or more optical elements,wherein each element may be a lens, a lens array, a filter or any otheroptical element, including opaque devices, mirrors and prisms. Alsooptical detectors such as bio-compatible CCD- or CMOS-chips areconceivable.

Another aspect of the present invention is an intraocular lens systemfor implantation in an eye comprising at least two varifocal lenses. Inone embodiments, the focal length of the lens system is dependent on atleast the rotation of the two lenses with respect to each other about anaxis which is substantially parallel to the main optical axis of thelens system and which is substantially stationary with respect to thetwo lenses. The intraocular lens system further comprises a frame forpositioning the lenses into the capsular bag of an eye such that onceimplanted the main optical axis of the lens system is substantiallyalong the optical axis of the eye. Thus the lens system may be kept inposition and preferably its lenses be kept free from contact (or haveonly limited contact) with the inner wall of the capsular bag. Further,the frame determines and maintains the optical axis of the system tothat of the eye, facilitating the lens design.

A combination of varifocal lenses, i.e. lenses which have different fociat different positions on the lens, may provide an optical systemexhibiting very large differences in its optical power upon very smallrelative linear and/or rotational displacements of the constituents.This makes it a preferred optical system for use as an intraocular lens,wherein small displacements are preferred to optimise the ratio thereofto the available volume of the capsular bag.

The frame may be arranged for causing a rotation of the two lenses withrespect to each other about an axis which has at least a componentparallel to the main optical axis of the lens system, and is preferablysubstantially parallel thereto, for changing the focal length of thelens system due to the natural action of the ciliary muscle on thecapsular bag of the eye. Thus, an accommodating intraocular lens isprovided.

Preferably the frame is arranged for causing at least a rotation of thetwo lenses with respect to each other about an axis which has at least acomponent parallel to the main optical axis of the lens system and ispreferably is substantially parallel thereto due to a displacement ofelements of the frame parallel to the optical axis of the eye. Such aframe does not rely on the equatorial motion of the capsular bag of theeye and thus may be free of contact with the equatorial rim thereof,which may reduce the chances of scarring or loss of flexibility of thecapsular bag.

The two lenses may be connected with a resilient element which isarranged for causing at least a rotation of the two lenses with respectto each other about an axis which has at least a component parallel tothe main optical axis of the lens system and is preferably issubstantially parallel thereto to the main optical axis of the lenssystem for changing the focal length of the lens system due to thenatural action of the ciliary muscle on the capsular bag of the eye. Aresilient connecting element may urge the lenses to a default position,enabling a well reproducible definition of an optical property of thelens system. A resilient element may also dose the displacement, sinceit may provide a countering force to the force of the ciliary muscleacting indirectly on the lenses, thus allowing a well-controllableaccommodation.

In a preferred embodiment, the two lenses are connected with a resilientelement which is arranged for causing at least a rotation of the twolenses with respect to each other about an axis which is substantiallyparallel to the main optical axis of the lens system due to adisplacement of elements of the frame substantially parallel to theoptical axis of the eye. Thus allowing to leave the equatorial rim ofthe capsular bag free from contacts which may exert stress on thecapsular bag and which may cause or aggravate inflexibility of thecapsular bag.

The lens system may be provided with at least one element for defining adefault configuration of at least the two lenses, thus allowing todefine and determine optical parameters such as the focal length of thelens system clearly and reproducibly.

Preferably, the focal length of the lens system in the defaultconfiguration is such that an eye wherein the lens system is implantedis emmetropic at the default configuration of the lens system. Thisprovides the patient with optimum vision at “infinity”. An emmetropicdefault configuration can also be reliably checked and possibly attainedduring or after implantation by allowing the ciliary muscle to relax,e.g. by letting the patient focus at an “infinitely” distant object orby a medicinal preparation or procedure, thus obtaining a referenceposition of the capsular bag.

Yet another aspect of the present invention is an intraocular lens forimplantation in the capsular bag of an eye having an optical axis,comprising an optical system and a frame. The frame comprises ananterior frame element, a posterior frame element, and a resilientelement for urging the anterior and posterior frame elements towards apredetermined axial separation. The frame further comprises a connectingelement connecting the anterior and posterior frame elements. Theoptical system is attached, in use, to the connecting element and isseparate from the anterior and posterior frame elements.

The predetermined axial separation should preferably be chosen such thatthe anterior and posterior frame elements are urged against the anteriorand posterior inner wall, respectively, of the capsular bag whenimplanted therein.

Thus, the optical system is free from contact with the capsular bag suchthat both the capsular bag and the optical system may be flushed withaqueous humor inside the capsular bag, thus reducing cell migration andgrowth and subsequent opacification thereof.

In some embodiments, a kit is provided for the implantation of anintraocular lens in the capsular bag of an eye, comprising abiocompatible material for filling the capsular bag, preferablysubstantially homogeneously, and replacing the natural lens tissue ofthe eye, and an intraocular frame. The frame comprises an anterior frameelement, a posterior frame element and a resilient element for urgingthe anterior and posterior frame elements against the anterior andposterior inner wall, respectively, of the capsular bag when implantedtherein, the frame being arranged for biasing the capsular bag towardsthe accommodating shape.

In this way, a natural lens may be emulated. The effective resiliencyand force of the artificial lens towards the accommodating shape may beselected by the material choice for the lens material and the resilientproperties of the frame, thus allowing to select an optimum combinationof properties for the assembly for implantation and use.

The frame, once implanted in the capsular bag of the eye, is preferablyin contact with the interior surface thereof on the anterior andposterior walls thereof and is free from contact with the equatorial rimthereof. Thus the capsular bag is essentially free from stress in theequatorial plane, and the natural force-balance of the eye may berelatively closely matched.

Preferably, at least the posterior frame element is provided with asharp edge along the contact region of the frame element with the wallof the capsular bag. This obstructs cellular migration from passingwithin a perimeter set by the sharp edge which may cause cellular growthand subsequent opacification and/or stiffening of the capsular bagwithin the contact region.

The frame, the lens and/or the optical system may be so configured thatparticular aspects thereof, such as the forces the different elementsexert to each other and/or to the capsular bag or optical parameterssuch as the focal length of a lens are adjustable prior, during and/orafter the implantation thereof. Further, any part may be formedfoldable, rollable generally deformable for insertion into the capsularbag with minimal damage.

In one embodiment, accommodating vision may be installed in a patient byimplanting an intraocular lens system or an intraocular lens into thecapsular bag of the eye after having removed the natural lens tissuetherefrom, or by implanting a frame according to an embodiment of thepresent invention and attaching an optical element thereto.

Additionally, accommodating vision may be installed in a patientfollowing the steps of removing the natural lens tissue of an eye, whileleaving the capsular bag essentially intact and implanting anintraocular frame comprising: an anterior frame element, a posteriorframe element, and a resilient element for urging the anterior andposterior frame elements against the anterior and posterior inner wall,respectively, of the capsular bag when implanted therein, the framebeing arranged for biasing the capsular bag towards the accommodatingshape, and filling the capsular bag with a biocompatible material forreplacing the natural lens tissue preferably substantiallyhomogeneously.

The thusly formed artificial lens enables natural-like accommodation.The opening or openings which has (have) to be made during the surgeryfor the removal of the natural lens and/or the insertion of the deviceor devices being implanted may be covered or closed with any knowntechnique such as suturing, gluing, covering with a biocompatiblematerial etc.

A suitable optical system for use with an embodiment of the presentinvention exhibits a varying focal power upon a relative rotation of thelenses. An effective optical system may be realised with two or moreappropriately formed varifocal lenses.

In some embodiments, a relatively straightforward method of determiningthe relevant shape of the lenses or determining relevant parameterstherefor has been discovered. The result is a rather simple equation forthe optimal shape of the lens profile. An accordingly shaped opticalsystem exhibits a very large focussing range for a relatively smallangular displacement. The change in focal length of the system inrelation to the rotation may be determined to suit a particular purposeor use.

According to an embodiment of the present invention, two lenses may beformed to contain a profile to form a compound lens system, comprised oftwo or more individual lenses, with optical power P, wherein the power Pis variable dependent on a rotation of both lenses by an angle, e.g. 2νradians, with respect to each other, e.g. ν rad in mutually oppositedirections with respect to a particular starting configuration, about asingle axis which is situated a distance, e.g. y₀, from the optical axisof the compound lens and which rotational axis is parallel to theoptical axis.

To determine a proper lens shape, consider two lenses extendingessentially parallel to each other and perpendicular to an axis z. Thethickness profile Δz, i.e. the variation of the lens thickness in thedirection z, as a function of position on the lens, of both lenses maybe expressed using a parameter A with the dimension (mm rad)⁻¹. Theparameter A, which is an amplitude of the profile Δz, determines alinear rate of optical power change with rotation ν.

In cylindrical coordinates (r,φ,z) the thickness profile Δz is given by:

Δz(r,φ)=−Aν{r ² cos² φ+(r sin φ−y ₀)²}.  (1)

The thickness profile Δz(r,φ) should preferably be symmetrical about arotation over ν radians. Thus the function z(r,φ) describing the profileof the surface of each lens should obey:

Δz(r,φ)=z(r,φ−ν)−z(r,φ+ν)  (2)

Eq. (2) may be transformed by taking the Taylor approximation to firstorder of the thickness profile Δz(r,φ) about φ for small ν. This yields:

z(r,φ−ν)−z(r,φ+ν)=Δz(r,φ)≈−2νd _(φ) {z(r,φ)},

wherein d_(φ){z(r,φ)} indicates the partial derivative to φ of z(r,φ).Substituting Eqs. (1) and (2) into Eq. and omitting constant termsresults in the following differential equation:

$\begin{matrix}\begin{matrix}{{d_{\phi}\left\{ {z\left( {r,\phi} \right)} \right\}} = {\frac{1}{2}{A\left( {{r^{2}\cos^{2}\phi} + {r^{2}\sin^{2}\phi} - {2\; y_{0}r\; \sin \; \phi}} \right)}}} \\{= {\frac{1}{2}{A\left( {r^{2} - {2\; y_{0}r\; \sin \; \phi}} \right)}}}\end{matrix} & (4)\end{matrix}$

Solving the differential equation (4) yields the following, rathersimple profile equation z(r,φ) for the surface profile of each lens:

z(r,φ)=½Ar ² φ+Ay ₀ r cos φ+E,  (5)

wherein E is an integration constant.

Eq. (5) may be extended with terms which superpose the surface profilez(r,φ) on another profile, but which do not influence the thicknessvariation Δz(r,φ) with respect to this profile per se:

z(r,φ)=½Ar ² φ+Ay ₀ r cos φ+Br+Cr ² +Dφ+E.  (6)

The parameters B, C, D and E in Eq. (6) may be used to optimise the lensprofile, e.g. to minimise the total lens thickness and/or to optimiseits optical quality.

The above derivation of Eqs. (5) and (6), respectively, may be extendedby including higher order terms of the Taylor expansion of Eq. (2), e.g.to further optimise the lens shape and reduce possible aberrations.

To calculate a suitable value for A, it may be observed that therelation between the power of a parabolic thin lens and the curvature ofits surface is generally defined as:

P=(n ₂ −n ₁)/R,  (7)

wherein P is the power of the lens in dioptre (Dpt), n₁, n₂ are theindices of refraction of the lens material and the surrounding material,respectively, and R is the radius of curvature of the lens surface inmillimetres.

For a lens having a surface given by Eq. (5), the lens power may bechosen to vary with A 2ν, as indicated above. Thus the relation betweenthe parameter A and the radius R of an equivalent spherical thin lens isgiven by:

R=(2Aν)⁻¹.  (8)

Thus the lens power P(ν) as a function of the rotation of the lenses isgiven by:

$\begin{matrix}\begin{matrix}{{P(v)} = {P_{0} + {2\; {A\left( {n_{2} - n_{1}} \right)}v}}} \\{{= {P_{0} + {\Delta \; {P(v)}}}},}\end{matrix} & (9)\end{matrix}$

wherein P₀ is the lens power for a default configuration with ν=ν₀ radmutual rotation between the lenses. Preferably, ν₀=0 rad. Conversely,for designing a particular compound lens the value of A may be chosenfrom:

$\begin{matrix}\begin{matrix}{A = {\left\{ {{P(v)} - P_{0}} \right\}/\left\{ {2\left( {n_{2} - n_{1}} \right)\left( {v - v_{0}} \right)} \right\}}} \\{{= {\Delta \; {{P(v)}/\left\{ {2\left( {n_{2} - n_{1}} \right)\Delta \; v} \right\}}}},}\end{matrix} & (10)\end{matrix}$

and substituting appropriate values for the intended purpose of the lenssystem.

For optical systems wherein the lens power is given by another equationthan Eq. (8), the derivation of an expression for P(ν) and A may beperformed analogously.

The parameter A need not be linear but may in itself also be a functionof one or more variables A(r,φ,z), dependent on the choice of thevariation of the lens power P with relative displacement of the lensesP(r,φ,z).

A convex-convex lens may have outer surfaces with a parabolic shape. Fora compound parabolic accommodating lens, the four surfaces are given bythe following equations (cf. Eq. (6)):

z ₃=½C ₃ r ² −C ₃ y ₀ r sin φ+E ₃.  (11)

z ₄=½Ar ² φ+Ay ₀ r cos φ+B ₄ r+C ₄ r ² +D ₄ φ+E ₄.  (12)

z ₅=½Ar ² φ+Ay ₀ r cos φ+B ₅ r+C ₅ r ² +D ₅ φ+E ₅.  (13)

z ₆=½C ₆ r ² −C ₆ y ₀ r sin φ+E ₆  (14)

wherein the surfaces of the lenses are identified with the numerals 3(anterior surface of the anterior lens), 4 (posterior surface of theanterior lens), 5 (anterior surface of the posterior lens) and 6(posterior surface of the posterior lens). B₄, C₄ and D₄ should be equalto B₅, C₅ and D₅, respectively for a cancelling of the thicknessvariation in a default position, preferably at ν=ν₀=0, and for ensuringa linear and consistent effect of the rotation. The values E₁₋₆represent the positions of the respective surfaces. In the case that z₄and z₅ are formed so that their focussing effects cancel at a rotationangle of ν=ν₀=0, z₃ and z₆ determine the default lens power. z₃ and z₆are mainly determined by the values of C₃ and C₆. For a symmetric lenshaving a mid-plane at z=0, z₃ and z₆ are mirror images with C₃=−C₆ andE₃=−E₆. Preferably C₃=−C₆=½R (cf. Eqs. (7) and (8)).

Such an optical system may be used for any purpose where an adjustablefocal lens shift is desired, inter alia for cameras, telescopes etc. Abenefit is that a substantial change in focal length may be achieved bysimply rotating one or two lenses in one plane. This requiressubstantially less energy and space than displacing a lens overappreciable distances along the optical axis of an optical system, aswith telescopes known in the art. Further, each rotating lens may beattached to a single common axis, allowing a proper and reliablerelative orientation essentially throughout the entire focussing range.

As an example, for calculating a compound lens for use as an intraocularlens in a human eye, the values according to the following Table 1 maybe used:

TABLE 1 values for calculating an intraocular accommodating lens. Baserefraction at accommodation, P₀ 32 Dpt Refraction at emmetropy, P_(emm)24 Dpt Diameter of each lens 5.5 mm Offset between optical/rotationalaxes, y₀ 3.5 mm Rotation for accommodation, per lens, v_(acc) ±0.10 rad= ±5.7° Refractive index of aqueous humor, n₁ 1.336 Refractive index oflens material PMMA, n₂ 1.498

Substituting the values of Table 1 in Eq. (10) it can be found that theoptical system exhibits the desired accommodation scope ΔP(Δν=0.10 rad)8 Dpt for A=0.247.

An optical system with the optimum combination of minimum lens thicknessand best optical quality may be obtained by inserting the values for Aand for y₀ into Eqs. (11)-(14), taking C₃=−C₆=½R, and optimising theother parameters, which may be done numerically.

A suitable result is summarised in the following Table 2:

TABLE 2 overview of suitable parameters for an accommodating intraocularlens according to an aspect of the present invention. Y₀  3.5 mm A 0.247/mm rad B₄ = B₅  0 C₃ = −C₆  0.0988/mm C₄ = C₅ −0.1940 mm D₄ = D₅ 1.0142 mm/rad E₃ = −E₆ −0.25 mm E₄ −1.82 mm E₅ −1.35 mm

The surfaces z₃ and z₆ may also be shaped to provide a non-rotationallysymmetric compound lens, e.g. for the correction of astigmatism, toreduce spherical aberration of the compound lens and/or improve off-axisoptical performance of an accommodative intra-ocular lens.

The thickness profile Δz(r,φ) of an aspheric lens may be described bythe following conic of revolution:

Δz(r,φ)=−cr ²/{1+(1−kc ² r ²)^(1/2)},  (15)

wherein c represents the curvature of an equivalent thin lens. Theasphericity of the surface is expressed by the conic constant k whichindicates the change in gradient of the surface (k<1: reducing gradient,flattening; k>1 increasing gradient, becoming steeper) with distancefrom the apex. k thus indicates the degree to which an aspheric thinlens differs from the equivalent spherical form. Depending on the valueof k, the lens surface is a hyperboloid for k<0, a paraboloid for k=0, aprolate ellipsoid for 0≦k≦1, a sphere for k=1, and an oblate spheroidfor k>1.

Using a Taylor approximation to the fourth order of Eq. (15) thefollowing expression is obtained:

Δz(r,φ)=−½cr ² −k/8c ³ r ⁴.  (16)

Eq. (16) and the differential equation Eq. (4) may be combined asindicated above.

Using a thickness profile with variable power according to c=2 A ν and aconic constant k the following relatively straightforward analyticalexpression, which contains the parameters A, y₀ and k, is obtained forthe profile z(r, φ):

$\begin{matrix}\begin{matrix}{{z\left( {r,\phi} \right)} = {{\frac{1}{2}{Ar}^{2}\phi} + {{Ary}_{0}\cos \; \phi} +}} \\{{{\frac{1}{2}A^{3}k\; \phi \; r^{4}} + {2\; A^{3}k\; \phi \; r^{2}y_{0}^{2}} + {\frac{1}{2}A^{3}k\; \phi \; y_{0}^{4}} +}} \\{{{2\; A^{3}{kr}^{3}y_{0}\cos \; \phi} + {2\; A^{3}{kry}_{0}^{3}\cos \; \phi} -}} \\{{{\frac{1}{2}A^{3}{kr}^{2}y_{0}^{2}\sin \; 2\; \phi} + {E.}}}\end{matrix} & (17)\end{matrix}$

It should be noted that the effective asphericity of the compound lensis dependent on the amount of rotation ν.

The surface profile in (17) may be extended with higher order terms forminimising thickness and optimising optical quality of the individuallenses and the compound lens.

The embodiments of present invention will hereafter be explained in moredetail with reference to the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B show a schematic cross-section of a frame and itsoperation according to an aspect of the present invention implanted intothe capsular bag of a human eye in both in accommodated and indesaccommodated state.

FIGS. 2A and 2B show a schematic cross-section of the frame implantedinto a capsular bag according to FIGS. 1A, 1B wherein the capsular bagis provided with a plug to close a rhexis.

FIG. 3 shows a schematic cross-section of the frame implanted into acapsular bag according to FIGS. 1A, 1B, wherein the capsular bag isprovided with a window to close a rhexis.

FIG. 4 shows a schematic cross-section of the frame implanted into acapsular bag provided with a window according to FIG. 3, wherein thewindow is provided with an additional lens.

FIGS. 5A and 5B show a schematic cross-section of a deformableintraocular lens attached to a frame and implanted into a capsular bagaccording to FIGS. 1A, 1B.

FIGS. 6A and 6B show a schematic cross-section of a deformableintraocular lens system attached to a frame and implanted into acapsular bag according to FIGS. 1A, 1B.

FIG. 7 shows a perspective side view of an embodiment of an intraocularlens according to the present invention.

FIG. 8 shows a front view along the optical axis of the embodiment ofFIG. 7.

FIG. 9 shows a perspective side view of another embodiment of anintraocular lens according to the present invention.

FIG. 10 shows a rear view of the intraocular lens of FIG. 9.

FIG. 11 shows a perspective side view from another angle of theintraocular lens of FIG. 9.

FIG. 12 shows a perspective side view from yet another angle of theintraocular lens of FIG. 9.

FIG. 13 shows yet another embodiment of an intraocular lens according tothe present invention.

FIG. 14 shows a graph of the simulated lens power vs. the rotation angleof the lenses of a lens system according to an embodiment of the presentinvention.

FIG. 15 shows a graph of the simulated lens power vs. the exerted forceon the lenses by the ciliary muscle of a lens system according to anembodiment of the present invention.

FIG. 16 shows a graph of the simulated modulation transfer function of alens system according to an embodiment of the present invention.

FIG. 17 shows a perspective side view of another embodiment of anintraocular lens according to the present invention.

FIG. 18 shows a perspective side view from another angle of theintraocular lens of FIG. 17, with the anterior part removed.

FIGS. 19 and 20 show constituent parts of the embodiment of FIG. 17.

FIGS. 21A and 21 show the operation of the optical system of theembodiment of FIG. 17.

FIGS. 22A and 22B show perspective side views of another embodiment ofan intraocular lens according to the present invention.

FIG. 23 shows a perspective side view from another angle of theembodiment of FIGS. 22A, 22B, with the anterior part removed.

FIG. 24 shows a variant of the embodiment of FIG. 23.

DETAILED DESCRIPTION

FIGS. 1A-6B show a schematic cross-section of a part of a human eye,which is substantially rotationally symmetric about the optical axis OA.The top side of the figures is the front or anterior side of the eye(marked “Ant.” in FIGS. 1A, 1B), the bottom side is the rear orposterior side (marked “Post.” in FIGS. 1A, 1B).

FIGS. 1A-6B show the ciliary muscle 1, the zonulae 2 and the capsularbag 3. A frame 4 is implanted in the capsular bag 3. The zonulae 2 areattached to the ciliary muscle 1 and the capsular bag 3 and connectthese.

The zonulae 2 are attached to the capsular bag 3 around its equatorialrim, which extends along the surface of the capsular bag forapproximately 2.5 mm anterior and posterior of the equatorial plane ofthe capsular bag 3 with respect to the optical axis OA. The equatorialplane is spanned by the line of maximum girth of the capsular bag 3 andthe ciliary muscle 1.

The frame 4 as shown comprises an anterior frame element 5, a posteriorframe element 6, two resilient elements 7, and two connecting elements 8which connect the anterior and posterior frame elements 5, 6. Theanterior and posterior parts of the connecting elements 8 are movablewith respect to each other, in FIGS. 1A-1B schematically indicated withrotational or flexible joints 9.

In certain embodiments, once implanted, the frame 4 is in contact onlywith the anterior and posterior walls of the interior surface of thecapsular bag 4, and is free from contact with the equatorial rim of thecapsular bag. In such embodiments, the capsular bag may be essentiallyfree from stress in the equatorial plane, and the natural force-balanceof the eye may be relatively closely matched. Accordingly, the overalldiameter of the frame 4 in a direction perpendicular to the optical axisOA and/or the diameter of each frame elements 5, 6 are selected toprovide this limited contact area within the capsular bag 4. In suchembodiments, the outer diameter of each frame element 5, 6 may bebetween about 5 mm and about 8 mm, or between 5.5 mm and 7.0 mm.Alternatively or additionally, the overall maximum diameter of the frame4 (e.g., between the flexible joints 9 in the illustrated embodiment)may be less than 10 mm, less than 9 mm, or even less than 8 mm or 8.5mm. In some embodiments, contact with the anterior and posterior wallsonly of the capsular bag 4 is provided by selection of the spacing alongthe optical axis OA between the outer portions of the frame elements 5,6 (e.g., the portions of the frame elements that contact the capsularbag 4). For example, the spacing along the optical axis OA between theouter portions of the frame elements 5, 6 when the frame 4 is in anunstressed state may be selected to be at least 4 mm, 5 mm, or 6 mm, theselection being influenced at least in part by the size of the capsularbag and whether the unstressed state of the frame 4 is intended toprovide an accommodated state or a disaccommodated state afterimplantation.

The connecting elements 8 may be integrated with the resilient elements7, as shown in the embodiments shown in FIGS. 2-13. In the shownembodiments the upper and lower arms of the connecting elements 8deflect away from one another along the optical axis OA.

When the ciliary muscle 1 is relaxed, the zonulae 2 are stretched tautand pull on the capsular bag 3, as shown in FIG. 1A. When the ciliarymuscle 1 is tensioned, it contracts so that its diameter reduces and thecapsular bag 3 may expand along the optical axis OA, as shown in FIG.1B.

In a natural eye the resiliency of the lens is essentially provided bythe lens tissue. Upon removal of the lens tissue this resiliency issubstantially lost. This loss may be at least partially compensated bythe resiliency of the frame 4.

The resilient elements 7 urge the anterior and posterior frame elements5, 6 against the anterior and posterior wall portions of the capsularbag 3 with sufficient force to bias the capsular bag 3 to anaccommodating shape upon contraction of the ciliary muscle 1. However,the force produced by the resilient element 7 is sufficiently weak suchthat the capsular bag 3 and the frame 4 can be flattened upon relaxationof the ciliary muscle 1 (as seen in FIG. 1A).

The resilient elements 7 may be formed of any kind of resilientmaterial, including massive rods or hollow tubes, or plastic or metallicsprings. For implantation in an eye the elements should be formedbiocompatible, e.g. by the material properties themselves or by beingcoated with a biocompatible material etc. The other parts of the framemay be formed analogously.

In some embodiments the function of the resilient elements 7 isincorporated into the connecting elements 8. In such embodiments aseparate resilient element 7 may be eliminated.

The edges of the anterior and posterior frame elements 5, 6 are providedwith a sharp edge along the rim forming the contact region of the frameelement 5, 6 with the inner wall of the capsular bag 3, serving toobstruct cellular migration across the inner wall of the capsular bag 3into the interior of the rim of the frame elements 5, 6.

In operation, tension in the zonulae 2 relaxes upon a contraction of theciliary muscle 1 and the frame 4 biases the capsular bag 3 to theaccommodating shape, as indicated with arrows in FIG. 1B. Thus, theanterior and posterior frame elements 5, 6 undergo a first displacementin a direction substantially along the optical axis OA. This causes asecond displacement of the connecting elements 8 in the form of astretching, whereby the joints 9 are displaced substantiallyperpendicular to the optical axis OA, as indicated with arrows in FIG.1B. The displacements of different points along the connecting elements8 comprise different contributions along and perpendicular to theoptical axis OA. The actual displacement of each point depends on theactual shape and possible resiliency of the connecting elements 9. Asused herein, the term “substantially”, when used to indicate approximateangular orientation (e.g., “substantially parallel”, “substantiallyalong”, “substantially perpendicular”, and the like) mean to within plusor minus 10 degrees.

The natural human eye lens is asymmetrical; the anterior half is flatterthan the posterior half with respect to the equatorial plane.Correspondingly, the joints 9 may be positioned offset from the middleof the connecting elements 8, or the resiliency of a resilient element 7may vary along its length.

In order to implant a frame 4 into the capsular bag 3 of an eye, thecapsular bag 3 has to be opened to form an opening 11. This opening 11,also called rhexis, should be sufficiently large so that the frame 4 maybe inserted into the capsular bag 3, yet be as small as possible toavoid complications such as ruptures, scarring etc.

FIGS. 1, 2 and 3 show that the rhexis 11 may be closed by in anysuitable way known in the art such as suturing or gluing (FIG. 1) by anartificial plug 12 (FIG. 2; plug not drawn to scale) or by a, preferablyflexible, window 13 (FIG. 3).

The closure of the rhexis 11 may serve to assist maintaining integrityof the capsular bag 3 and/or to maintain the contents of the capsularbag 3 therein. These contents may be aqueous humor, an artificialbiocompatible lens material emulating natural lens tissue or even thenatural lens tissue. The effective resiliency of the frame 4, which maybe expressed as a spring constant C_(s), may be configured to equal thatof a healthy, young natural lens.

In case the refraction of the contents is insufficient for properaccommodation, the window 13 may be integrated with a lens 14, as shownin the particular embodiment of FIG. 4.

It is, however, preferred that the rhexis 11 be left open at leastpartially to allow the exchange of aqueous humor between the anteriorchamber of the eye and the inside of the capsular bag 3. E.g. the plug12 of FIG. 2 may be designed to allow aqueous humor to pass but tomaintain a less-fluid implanted lens material inside the capsular bag 3.Further, an open rhexis allows to equate the interior pressure of theanterior chamber and the capsular bag during accommodation anddesaccommodation.

In the art it is known to excise a window from the anterior wall of thecapsular bag 3, in order to allow an essentially unobstructed flow ofaqueous humor through the capsular bag 3 which is thought to helpprevent cell growth and scarring of the wall of the capsular bag 3, asdiscussed supra. When using a frame 4, the reversible deformation of thecapsular bag 3 by the action of the ciliary muscle is maintained,causing the aqueous humor to flow and be exchanged due to a pumpingeffect.

The tissue forming the rim of the rhexis, especially in case of one witha rather large diameter, may become rather flabby which may influencethe behaviour of the capsular bag. This may be prevented to a relativelylarge extent by attaching the rim of the rhexis 11 to the anterior frameelement by any suitable technique, such as gluing, suturing, stapling,clamping or clasping etc. An additional element or ring outside thecapsular bag may be provided for this purpose. Similarly, a rhexiswindow 13, 14 may be attached to the frame, both with and without alsoaffixing the capsular bag tissue at the same time.

FIG. 5 shows an embodiment of an intraocular lens (hereinafter alsoreferred to as “IOL”) 15, comprising a frame 4 and a reversiblydeformable lens 16. The lens 16 is attached to the joints 9 of at leasttwo connecting elements 8 of the frame 4 by means of one or moreartificial zonulae 17. The lens 16 is resilient and preferably has arelaxed shape which is strongly curved or essentially spherical, similarto that of a natural lens. It is equally conceivable to realise the lens16 as a bag containing a reversibly deformable material such as amaterial of a resilient, visco-elastic, fluid or even gaseous nature.The connecting elements 8 may be resilient or not. In this latterconfiguration the resilient properties of the IOL 15 as a whole may bederived from the resiliency of the lens 16.

In operation the action of the ciliary muscle 1 on the capsular bag 3 istransmitted to the IOL 15, and via the frame 4 thereof to the lens 16.Conversely, the forces caused by the resiliency of the lens 16 and/orother elements of the IOL 15 are conveyed to the capsular bag and urgeit towards accommodation (FIG. 5B). Thus, an accommodating IOL isprovided which emulates the operation of a natural lens. The lens 16 isfree from contact with a wall of the capsular bag 3, so that allsurfaces may be rinsed by the aqueous humor.

FIGS. 6A and 6B show a schematic view of an embodiment of an IOL 15provided with an reversibly deformable compound lens 18 attached to aframe 4. The lens 18 is an optical system 18 comprising two opticalelements, in the form of two varifocal lenses 19, 20 which are movablewith respect to each other.

In operation the action of the ciliary muscle 1 on the capsular bag 3 istransmitted to the IOL 15, and via the frame 4 thereof to the opticalsystem 18, such that the lenses 19 and 20 are displaced with respect toeach other. In the shown embodiment, the lenses 19, 20 substantiallyfully overlap in the accommodating position FIG. 6B and are displacedwith respect to each other when the ciliary muscle 1 is relaxed (FIG.6A). The opposite situation of overlapping lenses 19, 20 for a relaxedciliary muscle 1 and displaced lenses for accommodation, or any otheroverlapping or non-overlapping arrangement may be constructedequivalently.

In the shown embodiment, the centres of both lenses 19, 20 aresymmetrically offset from the optical axis for a relaxed ciliary muscle(FIG. 6A). Asymmetric displacement is also possible, e.g. by mountingonly one lens movable to a connecting element 8 of the frame 4, byattaching both lenses to the same connecting element 8 or to parts ofconnecting element 8 exhibiting different displacement paths.

The lenses 19, 20 may be formed according to Eqs. (11)-(14) with theparameters of Tables 1 and 2, but other shapes or other optical objectsare also possible.

FIGS. 7 and 8 show a side view and a front view, i.e. seen on theanterior side, of a preferred embodiment of an IOL 21. The operation ofthe IOL is according to the principle indicated in FIG. 6.

The IOL 21 comprises a frame 22 and an optical system 23. The frame 22comprises an anterior frame element 24, a posterior frame element 25,first and second resilient connecting elements 26A, 26B to each of whichhaptics 27, 28 are attached. The first and second resilient connectingelements 26A, 26B deflect radially outward, relative to a straightconnection between the anterior and posterior frame elements 24, 25, bybeing bent.

The optical system 23 comprises a compound lens 29 in turn comprisingtwo varifocal lenses 29A, 29B. The lenses 29A, 29B are each attached tothe first or second connecting element 26A, 26B, by means of aconnecting arm 30A, 30B, respectively.

The arms 30A, 30B are attached to the resilient connecting elements 26A,26B at the position of their maximum outward deflection. The arms 30A,30B extend essentially radially with respect to the symmetry axis of thelens 29 and the frame 22 and are formed flexible and/or resilient.

The optical system 23 further comprises an interconnection 31 formutually movably interconnecting the lenses 29A, 29B. Theinterconnection 31 comprises arms 32A, 32B which are connected to eachlens 29A, 29B, respectively, and which are joined at joint 33.

The interconnection 31 provides additional stability to the relativeposition of the lenses 29A, 29B, inter alia to prevent the lenses fromtouching each other. The interconnection 31 further provides a centre ofrotation, at the joint 33, for the rotation of the individual opticalelements 29A, 29B with respect to each other. The axis of rotation issubstantially parallel to the optical axis of the optical system 23.

The joint 33 may be formed in any suitable manner, e.g. be the result ofthe entire optical system 23 or the entire IOL 21 being a monolithicobject. The joint may also be formed as a glued or welded connection orbe a hinge etc. In the embodiment shown in FIGS. 7, 8, theinterconnection 31, and thus the joint 33, is formed as a monolithicelement, attached to the lenses 29A, 29B.

Here, the interconnection 31 also forms a resilient element forproviding a restoring force for urging the elements of the opticalsystem 23 to a default configuration. The default position of the IOL 21as a whole, in the absence of external forces, depends on theinteraction of all its elements under the influence of the differentresilient elements 26A, 26B, 31. In the shown embodiment the lenses 29A,29B are substantially overlapping (FIGS. 7, 8). In this position thecompound lens 29 preferably has a lens power of approximately 32 Dpt,for providing a focal length for nearby vision.

Preferably, the IOL 21 is arranged or implanted such that the symmetryaxis of the frame and the optical axis of the optical system 23 coincidewith the optical axis of the eye, and the points or regions of bendingor flexing of the connecting elements 26A, 26B lie in the equatorialplane of the capsular bag. The connecting elements 26A, 26B are thusasymmetric with respect to the equatorial plane.

To account on the one hand for the asymmetry of the capsular bag of ahuman eye with respect to the equatorial plane and on the other hand forthe desired symmetry of the relative displacement of the lenses 29A,29B, the posterior sections of the resilient connecting elements 26A,26B, are provided with reinforcements 34A, 34B, respectively. Thereinforcements 34A, 34B counteract the fact that in this embodiment theposterior sections of the resilient elements 26A, 26B are longer thanthe anterior sections thereof, which would naturally lead to arelatively weaker spring force of the posterior section.

The haptics 27, 28 are provided for further assisting the positioning ofthe IOL 21 into the capsular bag of an eye, relative to the equatorialplane and the optical axis of both the eye and the IOL 21, and forassisting the maintenance of that position after implantation. Thehaptics 27, 28 are arranged for gently pressing against the equatorialrim of the capsular bag, preferably just sufficiently strong to maintainthe position of the IOL 21, but weak enough not to tension or stretchthe capsular bag.

The resiliency, shape and/or structural strength of each element of theIOL 21, including the lenses 29A, 29B, may be adaptable, e.g., byremoval of material to locally disassemble parts or to weaken or lightenthe structure, if so desired. Thus, the forces acting on the capsularbag may be tuned.

FIGS. 9, 11 and 12 show different side views of a second preferredembodiment of an IOL 21. FIG. 10 shows a rear view of this embodimenti.e. the IOL 21 is shown from the posterior side. In FIGS. 7, 8 and 9-12substantially equivalent elements are indicated with the same referencenumerals.

The first and second connecting elements 26A, 26B of the frame 22 areresilient. The four resilient elements 26A, 26B, 35, 36 are configuredfor urging the anterior and posterior frame elements 24, 25 against theanterior and posterior inner wall, respectively, of the capsular bag ofan eye when implanted therein.

The resiliency of the individual resilient elements 26A, 26B, 35, 36 andthe interconnection 31 is preferably chosen or adapted to result in asubstantially axial symmetric spring force on the anterior and posteriorframe elements 24, 25 upon compression thereof, and thus on the anteriorand posterior walls of the capsular bag of an eye when the IOL 21 isimplanted therein. Preferably, the IOL 21 is arranged or implanted suchthat the symmetry axis of the force coincides with the optical axis ofthe eye, and the points or regions of bending or flexing of theresilient elements 26A, 26B, 35, 36 lie all in the equatorial plane ofthe capsular bag.

These aspects may be designed and/or adjusted by the dimensions of theparts of the IOL 21, e.g. with the reinforcements 34A, 34B, 38, 39 onthe resilient elements 26A, 26B, 35, 36.

The interior edge of the anterior and posterior frame elements 24, 25are formed as sharp rims 40, 41 for urging into the wall of the capsularbag, to obstruct cellular migration thereunder.

In the second embodiment of FIGS. 9-12, the frame 22 comprises tworesilient connecting elements 26A, 26B, to which the optical system 23is attached, and two additional resilient elements 34, 35, which areonly attached to the anterior and posterior frame elements 24, 25 and towhich the optical system 23 is not attached. This embodiment does notcomprise haptics. Each lens 29A, 29B of this embodiment is furtherprovided with a stop 37A, 37B, respectively, the function of which willbe explained below.

In the shown embodiment, the joint 33 of the interconnection 31 betweenthe lenses 29A, 29B is formed by a fitting connection between the arms32A, 32B by a peg 33A of essentially square cross-section in a matchinghole 33B.

The arms 30A, 30B are attached to the connecting elements 26A, 26B in asimilar peg-in-hole fashion with a tight fit. This connection may beglued, welded or affixed in any suitable manner if necessary. Thus, theIOL is formed as a kit of parts for facilitating fabrication andimplantation of the separate components, viz. the frame, the anteriorlens and the posterior lens. However, the IOL may be formed andimplanted in more or less separate parts or as a single monolithicobject.

The interconnection 31 forms a resilient element for providing arestoring force for urging each lens 29A, 29B away from each other.Thus, in this second embodiment the lenses 29A, 29B are rotated withrespect to each other in the default configuration of absence ofexternal forces, which is shown in FIGS. 9-12. In this default positionthe compound lens 29 has a short focal length (high focal power) fornearby vision.

In this embodiment, the arms 30A, 30B which connect the optical system23 to the frame 22 are formed resilient and are arranged non-radially.

The arms 30A, 30B are attached to the lenses 29A, 29B such that theessential radial pulling force F1 (see FIG. 10) of the connectingelements 26A, 26B on the arms 30A, 30B causes, in combination with theeffective axis of rotation of the interconnection 31, an effectivedisplacement force F2 on the lenses 29A, 29B (see FIG. 10) which isessentially parallel to this radial pulling force F1. The force F2 thushas components both radial and tangential to the axis of symmetry of theframe and/or the entire IOL. As a consequence of this arrangement avariation in the deflection of the connecting elements 26A, 26B ismapped to a relative displacement of the lenses 29A, 29B. Thearrangement is preferably such that the mapping is unitarily, i.e. thedisplacement of the apex of the connecting elements 26A, 26B is equal tothat of the lenses 29A, 29B. This facilitates calculating and optimisingthe behaviour of the IOL.

A further effect of such an arrangement is that the optical axis of thecompound lens 29 may remain essentially immobile with respect to theframe upon a rotation of the lenses 29A, 29B.

When implanted in the capsular bag of an eye, a relative displacement ofthe anterior and posterior frame elements 24, 25 towards each othercauses a pulling on the lenses 29A, 29B along the arrow F2, resulting inthe lenses 29A, 29B the to be displaced towards an overlappingconfiguration. Further displacement beyond overlapping is arrested bythe lenses 29A, 29B engaging the stops 37B, 37A on the other lens 29B,29A, respectively. Thus a default configuration is determined.

The arrangement of the arms 30A, 30B also allows a decoupling of theframe 22 and the optical system 23 in the following sense: when theoptical system 23 is urged in the default configuration with the lenses29A, 29B engaging the stops 37B, 37A, further approaching of theanterior and posterior frame elements 24, 25 is enabled since aresulting displacement of the connecting elements 26A, 26B is absorbedby the resilient deformation of the arms 30A, 30B.

Thus, the overlapping default configuration of the compound lens 29 maybe achieved and maintained, whereas the frame 22 may still absorb aforce by the capsular bag. This second default configuration may berealised when the IOL 21 is implanted in the capsular bag 3 of an eyewherein the ciliary muscle 1 is fully relaxed.

In this second default configuration, which is essentially defined bythe combination of the IOL 21 and the eye of the patient, the focalpower of the lens 29 is preferably such that the eye is emmetropic.Since the details of each human eye are different, the IOL 21 may beadjustable to achieve this. Adjustments may be made by exchanging orreshaping (one of) the lenses 29A, 29B.

Further, the force balance of the IOL 21 may be adjusted, e.g. bylocally removing or ablating material from the interconnection 31, thearms 30A, 30B, the connecting elements 26A, 2613 and/or the resilientelements 35, 36. An IOL 21 which is implanted in an eye is consideredoptimally tuned when the effective forces on the lenses 29A, 29B are setsuch that with a fully relaxed ciliary muscle the lenses 29A, 29B arejust pulled free from the stops 37B, 37A.

The distance for proper focussing at nearby objects (fullaccommodation), e.g. for reading fine print or for detecting splintersin the skin, may generally be established at 10 cm from the eye. Thiscorresponds to an effective focal power of the lens of at fullaccommodation of P_(acc)≈P₀≈32 Dpt. Emmetropy is generally achieved forP_(emm)≈24 Dpt. The optical system may be designed, set to or adjustedto default configurations according to these values.

Preferably, the diameter of the optical system or of the lens, whetheror not a compound lens, is chosen such that the edges thereof areshielded by the iris such that distorted vision and aberrations such ascoma and glare, e.g. from oncoming traffic, are minimised. A suitablelens diameter for an average human adult is approximately 5.5 mm. Asuitable distance between the optical axis of such a lens and the centreof rotation in the case of the IOL 21 of FIGS. 6-12 is 3.5 mm. Thesesizes may of course be adapted to suit the individual to be treated.

For use in providing accommodating, the IOL preferably is able toprovide a change in optical power of at least about 0.25 Diopter perdegree of relative rotation between the lenses 29A, 29B, more preferablya change in optical power of at least 0.5 Diopter, 1 Diopter, or even1.5 Diopters per degree of relative rotation between the lenses 29A, 29B

The IOL 21 may also be sized such that the interconnection 31 or otherelements accessible from the outside by optical means such as a laserthrough the pupil when the iris has its maximum diameter. This allowsthe IOL 21 to be adjusted.

The different configurations of the connecting arms 30A, 30B also atleast partially determine the actual path of the displacement of thelenses 29A, 29B, and therewith a possible displacement of the effectiveoptical axis of the compound lens 29, as discussed above for theembodiment of FIGS. 9-12. E.g., for the IOL 21 according to FIGS. 7, 8,and according to Eqs. 11-14 with the values of Tables 1 and 2, thedeformation of the optical system 23 for a relative rotation of thelenses 29A, 29B of 0.10 rad, causes the rotational axis through thejoint 33 to move towards the symmetry axis of the frame 22. This causesan effective displacement of the optical axis of the compound lens 29 ofjust under 40 micron. This is considered acceptable for human use.

Due to the fact that the arrangement of the arms 30A, 30B of theembodiment of an equivalent IOL 21 according to FIGS. 9-12 also cause adisplacement with a tangential component, the displacement of theoptical axis between 0 and 0.10 rad rotation is below 10 micron, whichis not noticeable for most patients.

The distance between the rotational axis through joint 33 and theoptical axis of the compound lenses 29A, 29B (e.g., y₀) is preferablyless than the radius of the capsular bag on a typical human subject, forexample, less than about 6 mm, preferably less than 5 mm or less than 4mm. In some embodiments, this distance is even smaller, for example,within the radius of periphery of the lenses 29A and/or 29B (e.g., lessthan 3 mm or less than 2 mm). Furthermore, the overall size of the IOL21 is preferably configured to fit entirely within the capsular bag ofan eye of a subject. In the case of a human subject, for example, an IOLaccording to an embodiment of the present invention has a maximum extentin a direction normal to the optical axis thereof that is less thanabout 15 mm, preferably less than 12 mm, 11 mm, or 10 mm, depending onspecific construction of the IOL and the desired accommodativeperformance.

FIG. 13 shows a third embodiment of an intraocular lens, which issignificantly simpler in construction than the previous embodiments.

The IOL 42 comprises a frame 43 and an optical system 44. The frame 43comprises two frames halves 43A and 43B, respectively. Each frame half43A, 43B comprises an anterior frame element 45A, 45B, respectively, anda posterior frame element 46A, 46B, respectively, which are connected byresilient connecting elements 47A, 47B, respectively. The frame halves43A, 43B may be interconnected by additional elements, e.g. forming aring or a differently shaped closed rim as in the embodiments discussedbefore.

The optical system 44 comprises a compound lens 48, comprising varifocallenses 48A and 48B, respectively. The lenses 48A, 48B are mutuallymovable connected through interconnection 49. The joint 50 of theinterconnection 49 is shaped as a rotatable hinge 50 but may be of anysuitable construction.

The resilient connecting elements 47A, 47B of the frame 43 are veeredtowards the optical axes of the eye and the compound lens 48,respectively. The elements 47A, 47B are connected directly to the lenses48A, 48B, respectively, at the point of their maximum deflection from astraight connection. In FIG. 13 the connection is relatively broad, buta narrower connection or multiple connections at several positions arealso conceivable. Further, a movable connection such as a hinge or aflexible joint may be applied for allowing relative rotations between aframe half 43A, 43B and a lens 48A, 48B.

When implanted into the capsular bag of an eye, the reshaping of thecapsular bag as a result of the action of the ciliary muscle maycompress the frame 43 substantially parallel to the optical axis of theeye. This, opposite to the previously discussed embodiments causes thelenses 48A, 48B to be pressed, rather than pulled, towards another.

In the embodiment of FIG. 13 The lenses may be provided with stops fordetermining a default configuration of the optical system for emmetropy.Yet, in the embodiment shown in FIG. 13 with separate frame halves 43A,43B, the default configuration may be adjusted by simply repositioningthe frames halves with respect to each other inside the capsular bag.Preferably, after such adjustment the frame halves 43A, 43B are attachedor affixed to the capsular bag and/or to each other for additionalstability, security of the position and/or reproducibility of therelative motion and thus of the optical properties of the IOL 42.

The IOL 42 may also be provided as a kit of separate parts to beassembled prior or during operation, similar to the embodimentsdiscussed above.

A frame 4, 22 and/or an IOL 15, 21, 42 or any element thereof may beformed from one or more flexible or resilient materials so that it maybe compressed, folded or rolled to a shape with a smaller cross-sectionthan its natural shape. Thus the object may be inserted in the capsularbag 3 through a relatively small rhexis. The material may also be asomewhat gelatinous substance which sets to a firmer material underreaction with the aqueous humor, when exposed to body temperature orwhen irradiated with an appropriate wavelength, such as infrared orultraviolet radiation, etc. Such radiation may be delivered by laser,which also allows to provide local variations in the properties of thematerial. Laser irradiation may also be used to weld or even ablatematerial so as to assemble or adjust optical or generally structuralelements and/or properties thereof. A frame 4 and/or an IOL 15, 21, 42and/or elements thereof may be provided implantation-ready or as a kitof parts to be assembled. Such, and different, materials and procedureswhich may be performed prior, during or after insertion into an eye aregenerally known in the art.

In the shown embodiments the anterior and posterior frame elements 5, 6;24, 25 are annularly shaped, but may have any desired shape. It is,however, preferred that they are symmetrical, to provide a homogenousforce distribution on the capsular bag and to prevent it from damage.

FIGS. 14, 15 and 16 show the results of simulations, using commerciallyavailable ray-tracing and finite-element modelling software packets, ofan IOL 21 according to the embodiment of FIGS. 7-8 of the presentinvention. The simulated optical system consisted of two varifocallenses shaped according to Eqs. (11)-(14) and using the values of Tables1 and 2 supra.

FIG. 14 shows that indeed a substantially linear relation may beachieved between the relative rotation of the lenses and the resultingfocal power. From the results shown in the plot in FIG. 14, it is seenthat the IOL 21 provides a change in optical power of about 1.4 Dioptersper degree of rotation, for example, for a nominal lens power of about28 Diopters. This corresponds to about a 25 percent change in lens powerper degree of rotation.

FIG. 15 shows the result of modelling the effect of the net forceexerted by the zonulae on the capsular bag, integrated around thecircumference of the equatorial rim on the focal power of the IOL 21.The linear behaviour of FIG. 15 is the result of the fact that theentire IOL effectively acts as a single resilient element with a singleeffective spring constant of the system C_(s). Thus, the displacement ofthe lenses, and thus the optical power change, is also linear with theforce F exerted on the system, according to the spring equationF=−C_(s)U, wherein U is the amplitude of the extension (positive sign)or compression (negative sign) of the spring.

For this simulation the spring constant of the system is set to C_(s)=70mN/rad=12.3 mN/^(o) rotation per lens or C_(s)=242 mN/mm displacementper lens, relative to the frame. A stiffer IOL may have a higher springconstant C_(s), e.g. approx. 0.08 N/(full accommodation) which isconsidered a suitable value for use in a human eye. The spring constantmay be set by the material properties and the dimensions of the IOL orparticular elements thereof. The resiliency of the capsular bag may beneglected.

The approximation of a constant value for the effective spring constantof the entire system of frame 22 and optical system 23 is valid in theregion of elastically deforming and freely movable optical elements,thus as long as the lenses 29A, 29B are free from contact with any stopsand/or each other.

The actual values for an effective spring constant or other relevantnumerical parameters, such as sizes, weights, focal length etc. dependon the materials and structures used.

FIG. 16 shows the resolving power of the simulated compound lens 29 for0° relative rotation, i.e. for overlapping lenses and the optimum lenspower of 32 Dpt. For this, the modulation transfer function of thelenses is calculated. The modulation transfer function is a measure ofthe resolving power of an optical system observing an array of adjacentparallel sharp-edged black and white stripes with a particular spatialfrequency, and is given by

MTF=(I _(black) −I _(white))/(I _(black) +I _(white))  (18)

wherein I_(x) is the perceived intensity of the colour “X” at thedetector. MTF=1 equals perfect resolving power (individual black andwhite stripes are crisply detected), MTF=0 equals no resolving power;the array is perceived as a substantially homogeneously grey surface. Asmay be seen in FIG. 16 the lens performs better than a generally desiredbenchmark of at least MTF>0.4 for f_(spatial)=100 cycles/mm.

FIGS. 17 and 18 show another embodiment of an IOL, which is similar tothat of FIGS. 9-12 in both its basic construction and its functionality.The IOL 51 comprises a frame 52 and an optical system 53. The frame 52comprises individual frame parts 52A and 52B, comprising an anteriorframe element 52A′ and a posterior frame element 52B′, respectively, andhaving connecting elements 54. The connecting elements 54 compriseportions 54A, 54B being part of the anterior or posterior frame parts52A, 52B, respectively. The frame parts 52A and 52B are provided with acentral opening and with a relatively sharp edge for hindering cellmigration etc. The frame may be sized to remain free from the equatorialrim or to engage it.

The optical system 53 comprises a compound lens 55 in turn comprisingtwo individual varifocal lenses 55A, 55B.

FIG. 18 shows the IOL 51 from another view angle than FIG. 17 andwithout the upper frame half 52A for clarity.

The lenses 55A, 55B are each attached to a connecting element 54 by aconnecting arm 56A, 56B. The lenses 55A, 55B are mutually rotatinglyattached to each other by arms 57A, 57B at an interconnection joint 57.

As in the embodiments described above, the frame 52 is arranged forconverting a first displacement of the anterior and posterior frameelements 52A′, 52B′ essentially towards or away from each other, andthus towards or away from the centre of the frame 52, into a seconddisplacement of (the joints 58 of) the connecting elements 54 having atleast a component perpendicular to the first displacement, towards oraway from the centre of the frame 52.

For the IOL 51 the parts 52A, 52B, 55A, 55B are formed individually asshown in FIGS. 19 and 20, respectively and the parts 52A, 52B and 55A,55B may be substantially identical. Thus, the IOL 51 is essentiallymodular. This facilitates manufacturing of the IOL 51, since relativelysimple molds may be used, which may also facilitate separation of themold and the molded part. Parts may be assessed for quality individuallyand parts may be readily adapted and/or exchanged. It also facilitatesusing different materials for parts of the frame 52 and/or of theoptical system 53.

For forming an IOL 51, the parts 52A, 52B, 55A, 55B are assembled bymeans of the joints 57, 58, which may be freely pivotably hinging toessentially rigid, e.g. glued, riveted, or of the peg-in-hole type (cfjoint 33 of FIGS. 9-12), etc. The joints may also be snap-fittingjoints, wherein one part is provided with a portion, such as a clamp ora recess, for receiving a corresponding portion, e.g. an extension or aprotrusion, of another part. The movability of the joints 57, 58 and theresiliency of (portions of) the parts determines the spring constant ofthe frame 52, the optical system 53 and thus the IOL 51 as a whole; theconnecting element parts 54A, 54B and/or the anterior frame element 52A′and posterior frame element 52B′ themselves may be the resilient elementfor urging the anterior and posterior frame elements towards apredetermined axial separation.

Here, the joints 57, 58 are indicated as hinges with a pivot 59, 60,respectively. The frame parts 52A, 52B are rigidly or movably attachedto the pivots 60. The lenses 55A, 55B may be movably or rigidly attachedto the pivots 59, 60, depending on the resiliency of the arms 56A, 56B,57A, 57B and/or the torsional resiliency of the pivots 59, 60. Theconnecting elements 54A, 54B and/or the pivots 60 may be provided withan extension for attaching other objects thereto and/or for forminghaptics.

The lenses 55A, 55B are provided with stops 61A, 61B, which each have aresilient extension which is essentially free, not being directlyattached to the lenses 55A, 55B (FIGS. 18, 20). These stops serve adouble function, as will be explained with reference to FIGS. 21A, 21B,which shows the optical system 53 without the frame 52 in two differentpositions. The optical system 53 has a default position (FIG. 21A) inwhich the lenses 55A, 55B are only partially overlapping and the stopsjust make contact with each other. For changing the focal length of thesystem, the lenses are pulled (indicated with the arrows in FIG. 21B) torotate towards fully overlapping and possibly even further (FIG. 21B).Thereby, the resilient extensions of the stops 61A, 61B are urgedagainst each other, causing them to deflect and to provide a restoringforce for the optical system 53 and thus for the entire IOL 51 towardsthe default position (FIG. 21A). Since in this embodiment the pullingforce is essentially along a heart line of the optical system 53, thearms 56A, 56B may flex somewhat between the position shifts (FIGS. 21A,21B). This may cause an additional restoring force for the opticalsystem 53.

The optical system 53 and the stops 61A, 61B may also be sized anddesigned for a default position with the lenses 55A, 55B essentiallyfully overlapping and such that the lenses 5A, 55B should be moved awayfrom each other for changing the effective focal length of the compoundlens 55.

FIGS. 22A-23 show an embodiment of an IOL 62 which is similar to FIGS.17, 18. Here, the same frame 52 is provided with another optical system63, which comprises a compound lens 64, in turn comprising twoindividual varifocal lenses 64A, 64B. The compound lens 64 is designedfor changing its effective focal length upon an essentially linearrelative repositioning of the lenses 64A, 64B, rather than upon arelative rotation. For assisting that, the lenses 64A, 64B are providedwith extensions 65A, 65B comprising guiding structures whichinterconnect the lenses 64A, 64B and which define a relative motion pathfor the lenses 64A, 64B. The displacement is in a direction which issubstantially perpendicular to the main optical axis of the lens systemaxis.

The guiding structures may be formed as one or more protrusions and amatching groove or ribs with facing sliding surfaces, possibly profiledor hooking into each other etc. Stops and/or end points of the guidesmay define one or more default relative positions of the lenses 64A,64B. The lenses 64A, 64B may be essentially identical, allowing to use asingle mold for the lenses.

FIG. 24 shows a variant of FIG. 23, wherein the optical system 63 isprovided with additional resilient elements 66, e.g. springs, forproviding a restoring force towards a default relative position of thelenses 64A, 64B.

The frame 52 may be provided with additional connecting and/or resilientelements. The frame 52 may also be formed or assembled without providingit with an optical system, by just assembling the anterior and posteriorframe parts 52A, 52B. Such a frame 52 may be used on its own for biasingthe capsular bag 3 towards the accommodating shape, e.g. in combinationwith filling the capsular bag with a biocompatible material forreplacing the natural lens tissue.

Embodiments of the invention are not restricted to those described aboveherein, but may be varied in a number of ways, for example, as generallyexpressed by the following claims. For instance, the lenses may have anyshape.

The lenses may also be displaced linearly with respect to each other,e.g. by providing lenses with two rotational or resilientinterconnections on opposite sides or with a guiding rail etc.

The optical system may also comprise one or more separate opticalelements for correcting astigmatism, or elements for correcting otherimaging defects, such as coma or chromatic aberration.

The frame may comprise any useful number of resilient and/or connectingelements and/or of optical elements attached thereto. A torsional springmay also be adjustable by means of a reinforcement.

The frame may also be realised or provided with medically activesubstances, e.g. slow-release ingredients such as medicines.

Elements and aspects of different embodiments may be suitably combined.

1-36. (canceled)
 37. A frame for an intraocular lens, comprising: ananterior frame element and a posterior frame element, the frame elementsdisposed about an optical axis; and a connecting element for operablycoupling the frame elements to first and second optical elements; theconnecting element configured to convert a first displacement betweenthe frame elements in a direction that is substantially parallel to theoptical axis into a second displacement between the optical elementsthat is substantially perpendicular to the optical axis.
 38. The frameaccording to claim 37, wherein the connecting element is a resilientelement.
 39. The frame according to claim 37, wherein the deflection ofthe connecting element has a radial component with respect to theoptical axis of the eye.
 40. The frame according to claim 37, wherein atleast the anterior frame element provides an opening for allowingaqueous humor to pass therethrough.
 41. The frame according to claim 37,whereby at least the posterior frame element is provided with arelatively sharp edge along the contact region of the frame element withthe wall of the capsular bag.
 42. The frame according to claim 37,further comprising elements for substantially centering the frame aboutthe optical axis of the eye when implanted therein.
 43. The frameaccording to claim 37, wherein the frame is sized for being, onceimplanted in a capsular bag of an eye, in contact with the interiorsurface of the capsular bag on the anterior and posterior walls thereofand being free from contact with the equatorial rim thereof.
 44. Theframe according to claim 37, wherein the net effect of the forces on thecapsular bag is to generally urge the capsular bag towards theaccommodating shape.
 45. An intraocular lens for implantation in thecapsular bag of an eye, comprising: a frame disposed about an opticalaxis comprising an anterior frame element and a posterior frame element;a first optical element and a second optical element; and a connectingelement operably coupling the frame elements to the optical elements;the connecting element configured to convert a first displacementbetween the frame elements in a direction that is substantially parallelto the optical axis into a second displacement between the opticalelements that is substantially perpendicular to the optical axis. 46.The intraocular lens according to claim 45, wherein one of the opticalelements is coupled to a second connecting element of the frame.
 47. Theintraocular lens according to claim 45, wherein the first and secondoptical elements are varifocal lenses and the optical elements togetherhave a combined focal length that depends on a rotational and/or lineardisplacement between the first and second optical elements to oneanother in a direction that is substantially perpendicular to theoptical axis.
 48. The intraocular lens according to claim 45, furthercomprising an interconnection for providing a centre of rotation for atleast two individual optical elements with respect to one another. 49.The intraocular lens according to claim 45, further comprising a guidefor providing a substantially linear displacement of at least twooptical elements with respect to one another.
 50. The intraocular lensaccording to claim 45, wherein the optical elements define a defaultconfiguration in which an eye is emmetropic.
 51. The intraocular lensaccording to claim 45, wherein the optical elements define a defaultconfiguration in which a capsular bag into which the intraocular lens isplaced is in an accommodating shape.
 52. The intraocular lens accordingto claim 45, wherein, when the intraocular lens is placed in a capsularbag of an eye, the resilient element provides a restoring force forurging the optical elements to a default configuration that urges thecapsular bag towards an accommodating shape.
 53. The intraocular lensaccording to claim 45, wherein the combination of the first and secondlenses have a focal length that is dependent on at least a rotation ofthe lenses with respect to one another about an axis that issubstantially parallel to the optical axis of the lens system.
 54. Theintraocular lens according to claim 53, wherein the frame is configuredto cause the rotation of the lenses, the rotation being due to thenatural action of the ciliary muscle on the capsular bag of an eye intowhich the intraocular lens is implanted.
 55. The intraocular lensaccording to claim 45, wherein the frame has a maximum diameter in adirection perpendicular to the optical axis that is less than 10 mm and,when the frame is in an unstressed state, the spacing along the opticalaxis between outer portions of the anterior and posterior frame elementsis at least 4 mm.
 56. The intraocular lens according to claim 45,wherein the frame is sized for contacting the capsular bag of an eyewhen implanted therein only on the anterior and posterior walls andbeing free from contact with the equatorial walls.
 57. An intraocularlens for implantation in the capsular bag of an eye, comprising: a framedisposed about an optical axis; a first optical element and a secondoptical element; a connecting element operably coupling the frame to theoptical elements; and a joint disposed about a rotational axis, theoptical elements configured to rotate with respect to one another aboutthe rotational axis; the intraocular lens configured to be containedentirely within a capsular bag of an eye of a subject.
 58. Theintraocular lens of claim 57, wherein the subject is a human subject.59. The intraocular lens of claim 57, wherein the intraocular lens has amaximum extent in a direction normal to the optical axis that is lessthan 11 mm.
 60. The intraocular lens of claim 57, wherein the distancebetween the optical axis and the rotational axis is less than 5 mm.